1. Field of the Invention
This invention relates to welding apparatus and in particular, to a welding apparatus able to follow and weld an elliptical seam.
2. Description of the Prior Art
It is well known that in the fabrication of miter joints in metal cylindrical vessels, it is a difficult and time consuming task to properly weld the elliptical joints formed by the miter. Such welding problems usually arise in the fabrication of steam turbine systems where it is required that piping make severely angled turns in order to conduct fluid from one part of the system to another.
In the past, once a miter end of a pipe has been prepared and properly beveled it is necessary to hand weld the elliptical seam presented by the geometrical configuration of the elements. This is both time consuming, expensive and leads to the possibility of welding imperfections which jeopardize the security of the weld.
The provision of an apparatus to accomplish the welding process requires at a minimum the provision of means for rotation the member to be welded at a particular predetermined constant speed relative to the welding torch, and further, in order to avoid runoff of weld material, it is necessary to provide suitable means for tracking the highest point on the elliptical member relative to a fixed horizontal datum. This highest point is known in the art as the "top dead center" point. Such tracking means must be coordinated with means for displacing the welding torch so as to always maintain the torch adjacent this so-called "top dead center" point.